This invention relates to improvements in the construction of a rotary disc-type regenerator for an automotive gas turbine engine. In more detail, the invention relates to improved means for attaching the relatively rigid metal ring gear to the ceramic regenerator core.
One common disc-type regenerator comprises a core or matrix having a multitude of parallel axially extending gas passages arranged about a central hub or axis of rotation and confined within a peripheral rim. The axially opposite ends of the gas passages are arranged in parallel planes perpendicular to the axis of rotation and comprising end faces of the matrix through which two oppositely directed streams of gas at different temperatures and pressures are conducted. For example, a sector shaped seal in sliding and sealing contact with each of the opposite end faces of the regenerator matrix partitions the latter into two sectors. Comparatively cool high-pressure inlet air is directed toward one end face of the matrix at one sector thereof, thence through that sector to be preheated by the hot regenerator matrix. The preheated air is then directed to a combustion chamber where fuel is added and burned, the hot combustion products being then directed through the turbine stages of the engine to drive the turbine rotors.
The comparatively hot low-pressure exhaust gases from the rotors are then directed through the other sector of the regenerator matrix in the direction axially opposite to the inlet air flow, whereby the latter regenerator matrix is heated. Rotation of the regenerator carries its heated sector continuously to the region of the first mentioned sector to receive the comparatively cool gas flow to preheat the inlet gas as aforesaid, and thereby to cool the regenerator.
Such a regenerator is commonly known as a counterflow regenerator and is feasible for use in automotive gas turbine engines. Rotation of the regenerator is accomplished with a power driven pinion which meshes with an annular ring gear carried by an annular rim on the regenerator. Attachment of the relatively rigid metal ring gear to the ceramic regenerator core has been a problem. Due to simplicity and commercial availability, use of an elastomeric pad bonded to both the ceramic core and the metal rim to attach the ring gear to the core appears to be a simple and attractive solution to the problem. Unfortunately, during the process of development of bonding procedures, various failures and subsequent tests indicated that the elastomeric material in addition to shrinkage during curing and aging is expanding and contracting depending on surrounding temperature. Since the bond quality between elastomer and ceramic, and elastomer and metal jacket has been significantly improved, it was not unusual to find that parts of the matrix at the O.D. were broken away from the rest of the core. Apparently the tensile force exerted on the matrix by shrinking elastomer exceeded the strength of the matrix.